Since the time of the early reeves in England, when help was needed to apprehend a criminal, a hue and cry could be made to enlist support with law enforcement efforts. The tradition followed the sheriff to the New World and it would become a foundation of law. As well as being a basis of law, it became a stimulus which would capture the imagination of the American people and serve to inspire their will with regards to law and order. It invested the citizens in the law enforcement process and served to extend the office's usefulness by enabling and allowing for unlimited manpower resources at times of greatest need. In America the latin term "posse comitatus" was used to describe this volunteer effort. Literally translated, posse comitatus means "the power of the county". The authority of the posse comitatus was acquired through the powers of the office of sheriff and allowed the sheriff to recruit any person over the age of fifteen to aid in keeping the peace or to assist in the pursuit of felons. These efforts could be made with the presence of, or the absence of the sheriff. Much of the philosophy of law regarding citizen's arrest powers are founded in the posse comitatus premise.⁶⁵

During the War of 1812, the power of the posse comitatus was used in an incident that indirectly resulted in the writing of America's national anthem. When the British Army marched on Washington they passed through Upper Marlborough, Maryland. The local residents there were cooperative with the invading Army and in exchange for their cooperation little damage was done to the residents. After the battle of Bladensburg and the burning of Washington, the British army marched back through Upper Marlborough, but this time the troops were a bit more rambunctious. The soldiers looted local properties and set fire to some of the homes in the community.⁶⁶

A local resident, Dr. William Beanes, was so angered by the situation that he gathered a group of associates and headed a body of Upper Marborough citizens to take up arms and responded to a hue and cry to arrest the marauders. The posse comitatus tracked the a group of soldiers to a local tavern where they had been drinking and making quite a commotion. Vested with the powers to make a citizen's arrest, the posse rounded up the gang of ruffians and placed them in the custody of the sheriff at the Upper Marlborough jail. This information was quickly transmitted back to the British camp where the action of Dr. Beanes was not well received. The British commander dispatched orders to arrest Dr. Beanes and his posse.⁶⁷

Dr. Beanes and others were arrested and held for ransom on a British warship in Baltimore Harbor. A prisoner exchange was suggested that would involve Dr. Beanes and his group being exchanged for the release of the British soldiers that were awaiting trial in the Upper Marlborough jail. As Dr. Beanes was, what we would consider in today's parlance, "politically influential", a choice team of ambassadors was sent to negotiate his release. One was a United States government agent and the other was a brilliant young lawyer named Francis Scott Key. Key held some influence himself and was brother-in-law of the Chief Justice of the Supreme Court, Roger B. Taney. During the several days of negotiations to seek the release of Dr. Beanes and the posse, Francis Scott Key witnessed an attack on Fort McHenry. Standing on the deck of an American ship, Key looked through a telescope and observed the fighting. Seeing that the American flag was still there meant that the British had failed in their attack on Baltimore. He was so overwhelmed by the sight that he was inspired to express his feelings in verse which was to become The Star Spangled Banner.

The posse comitatus would become shortened to a vernacular version of just "posse". The American posse would become a mainstay of law enforcement discharge in the years to come. It would be employed to a great extent in the American Wild West period as a regular tool of marshals and sheriffs. The American posse would become romanticized in dime store novels and newspapers throughout the era. In later years it would again be romanticized in movies and television programs. The posse continues to be used in contemporary terms and still serves useful law enforcement purposes in many parts of the United States.